Patent GB-541545-A (GB)
Title: Colour photography and kinematography
IPC: G03C7/26
Filed: 1941-03-26
Abstract: 541,545. Colour photography and kinematography. TULL, A. G. March 26, 1941, No. 10035. Divided out of 540,975. [Class 98 (ii)] Sensitive material for recording or copying of the kind comprising a base coated with silver halide emulsion, different layers or strata of which are differently colour sensitive, the layer or stratum nearest the base being sensitive to red (or green) and diffusely coloured with a yellow (or magenta) dye capable of local destruction under control of a silver salt image formed therein, and the other layers or strata being substantially colourless, is processed after exposure by developing the latent images, and without fixing converting the developed images in the uncoloured layers into intermediate bodies for chemical toning, simultaneously or successively treating these images in a toning bath containing two reagents which tone said images to different colours, and treating the material in a dye-destruction bath to form a colour image in the dyed layer under control of the silver salt image therein. Materials described consist of (1) transparent, translucent, or opaque support, red-sensitized yellow-dyed emulsion layer, red filter (if desired), colourless greensensitized emulsion, yellow filter (if desired), and colourless blue sensitive emulsion, and (2) material similar to (1) but having a colourless red-sensitized middle layer and a magenta-dyed green-sensitized lowermost layer with a green filter (if desired) therebetween. These materials may be processed to negatives in colours complementary to those of the original, and positives may be printed therefrom, e.g. on similar material. In processing the negative the developed silver images may be converted into silver ferrocyanide as in a bath of potassium ferrocyanide and ammonia. The top two layers may then be subjected to a mixed bath containing a ferric salt and a uranium salt whereby the top image is toned to Prussian blue and the middle image to uranium ferrocyanide, as described in Specification 540,971. The toning agents may, if desired, be included in the bleaching bath. The negative image in the pre-dyed layer is produced at a stage in the processing in which the image in the layer exists as silver, by treatment with a bath which destroys the dye at the places where silver is not present, e.g. one containing calcium hypochlorite and acetic acid. The uranium ferrocyanide in the middle layer may be converted into a dye toned red or yellow image, e.g. after first converting it by a soluble zinc salt into zinc ferrocyanide which serves to mordant the dye, as described in Specification 540,979. The final step is the removal of silver images and any remaining silver salts as with Farmer's reducer. Material intended for prints may have a stripping layer between the emulsion layers and the base to permit transfer of said layers to a new support, as described in Specification 540,977; or the layers may be on an opaque or translucent support or there may be interposed between the layers and the support a layer which is either opaque, or is transparent but capable of being rendered opaque, e.g. as described in Specification 540,976.